The present invention relates to a method for exchanging data between a number of data processors which are connected to each other by one or more common data buses. More particularly, the present invention relates to a method of exchanging data in which the organizational measures required for the sequential flow of the data between the several processors are distributed uniformly among all the processors.
Processor-interconnection methods which exchange data via common data buses are known. In these methods, access to the communication channel (the data buses) is controlled by a central exchange, utilizing either a time-consuming exchange of interrogation and reply messages or additional signal conductors in order to exchange the useful information. The primary disadvantage of such centrally controlled communication systems is that the entire system fails whenever the central exchange fails. This drawback is sometimes overcome by introducing redundant exchanges. However, the switching mechanisms required on failure of the central exchange present problems themselves since the switching mechanism is prone to disturbance and messages may be lost on switching.
Processor-interconnection methods are also known in which the subscribers or processors are connected by ring- or loop-type data buses and in which the necessary organizational functions for sequentially processing data traffic are decentralized. In such methods, the organizational functions are uniformly distributed among all the subscribers. However, the known methods do not satisfy the condition that a message can be transmitted with protection against errors and losses, from any desired subscriber to any chosen number of other subscribers more or less simultaneously. This condition must however be satisfied in data systems in which not only is the acquisition of data to proceed in a decentralized manner, but also evaluation of one and the same message is sometimes required to proceed in a number of processors simultaneously.